In Vitro

Six soft-eyed young rabbits, all dark grey, hopped nonchalantly about their pen in Harvard's Laboratory of General Physiology last week as many a biologist discussed their twisted pedigree. They were living evidence of what two experimenters had reported as "the first certain demonstration that mammalian eggs can be fertilized in vitro."

In vitro (in glass ) is the polite name for methods by which physiologists impolitely try to fertilize ova removed from a female with sperm removed from a male. Such experiments have long been successful with forms of life lower than mammals. But attempts at external fertilization of rabbit eggs, though sometimes yielding the characteristic first signs of impregnation, never brought to birth any young.

Dr. Gregory Goodwin Pincus and his associate refined their operative procedure, gave their performers every advantage. The agouti* doe which was to contribute the ova was first allowed to mate with a sterile buck. After removal the ova, examined to make sure they were not fertilized, were placed in a culture flask for 20 min. with the healthy sperm of a non-agouti black buck. Finally they were implanted in the right Fallopian tube of a New Zealand Red doe which had been rendered pseudopregnant by a sterile mating. The dark grey color of the bunnies, born 33 days later, was proof they did not owe their existence to an accidental fertilization of their red foster-mother.

*Agouti: bavins black hair with yellow tips.

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